Boat lifts as shown in U.S. Pat. Nos. 2,976,694 Stanford, 3,177,668 Schneider, 3,362,172 Rutter, 3,753,355 Knock, 4,019,212 Downer, and 4,027,492 Carpenter have been found to be inadequate to meet the needs of boat owners who wish to quickly and easily lift these boats out of the water and launch them with the same ease and speed. The need for lifting ease and speed requirements may range from simple convenience to difficult conditions induced by high waves, fast currents or heavy winds.
Further, the above lifts are capable of raising a boat only a few feet while many lakes and dams may periodically rise and fall five, ten or even fifteen or more feet due to hydroelectric power generation and re-generation by refilling the lake during off peak power generation hours. Even major lakes such as Lake Tahoe on the border of California and Nevada are subject to a 6 foot change in water level. Rivers and flood control dams or sea coast waterways subject to tides can rise and fall several feet and render all but the largest lifts useless at low water conditions.
The increase in the number of boats and the need to maintain clear channels has made it impossible in many locations to install the prior art devices which are set on the bottom of the lake or river and remain submerged in the water when not lifting a boat. Such apparatus is a hazard to other boats and cannot be used where a clear channel is required.
All of the prior art lifts except Stanford, supra require "head-in" docking as opposed to the simpler and safer "parallel to pier" docking. The Stanford pivoting boat beacher is a "walking" pier, however, as well as a lift and is in a different category from simple lifts.
Finally, probably none of the above prior patented lifts can operate in water as shallow as the lift of the present invention, with the exception of Stanford, supra which can actually be driven on its crawler wheels up onto the beach.